JP3015805B2 - Metal pipe bending method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for bending a metal tube while uniformly heating the metal tube with a high-frequency induction heating coil.

[0002]

2. Description of the Related Art Generally, a metal tube is bent by hot bending using a high-frequency induction heating method. That is, as shown in FIG. 3, the metal tube 1 is inserted into a high-frequency induction heating coil 2 provided with a nozzle for spraying the cooling liquid 3, and a distal end portion thereof is clamped to a bending arm 4 pivoting about a fulcrum 0 with a clamp 5. The metal tube 1 is advanced while heating the metal tube 1 to an annular narrow width by the heating coil 2, and the bending arm 4 turns to apply a bending moment to the heating softened portion to bend and deform. Is cooled by the cooling liquid 3 to solidify the bending deformation portion.

However, in such high-frequency induction heating bending, a tensile stress acts on the outer peripheral side (back side) of the bending deformation to reduce the wall thickness, and a compressive stress acts on the inner peripheral side (bent side) of the bending deformation. As a result, the thickness increases, and a thickness difference occurs. This thickness difference causes a temperature difference in the circumferential direction. In addition, the positional relationship between the heating coil 2 and the metal tube 1 changes due to phenomena such as the appearance of the metal tube being formed into a flat shape that is long vertically and horizontally short by processing, and the metal tube itself moving depending on the bending direction. This also causes a temperature difference. Due to these temperature differences, the structure of the metal after bending becomes non-uniform, and there is a concern that the strength may be locally reduced.

As a countermeasure against these problems, Japanese Patent Application Laid-Open No.
No. 425 is disclosed as a prior art document. This is a processing temperature control method that detects the temperature of the back side and the ventral side of bending deformation and decenters the metal tube and the heating coil so that the temperature difference becomes a predetermined temperature difference. A detector for detecting the temperature of the heating part on the back side of the bending deformation and the belly side of the bending deformation, a calculator for calculating the temperature difference from the output difference of the detector, and a temperature difference setting device for inputting a desired temperature difference There is a processing temperature control device including a high-frequency induction heating coil and a coil movement control unit that relatively eccentrically moves the metal tube in and out of bending in accordance with a deviation between the calculated temperature difference and the set temperature difference. . If control is performed to make the temperature difference of this device zero, the temperature on the ventral side and the temperature on the dorsal side should match, but the temperature itself will vary with the thickness of the metal tube and the metal tube during processing. There is a possibility that the metal will oscillate in the direction of the processing axis due to movement or the like. Therefore, the structure of the metal after processing becomes non-uniform, and the possibility of local decrease in strength still remains.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for controlling the temperature of a metal tube to be heated in a circumferential direction to a target temperature when the metal tube is bent while being heated by a high-frequency induction heating coil. It is an object of the present invention to provide a method and an apparatus for bending a metal pipe, which can make the structure uniform.

[0006]

One of the methods for bending a metal tube according to the present invention for solving the above problems is to bend the metal tube while heating it with a high-frequency induction heating coil. The temperature of either the ventral side or the dorsal side of the bending deformation of the heating section is maintained at the target temperature by controlling the high-frequency heating power, and the difference between this target temperature and the temperature at the facing position is taken. The position of the high-frequency induction heating coil is controlled by the difference, the circumferential temperature of the heating section of the metal tube is made equal to the target temperature over the entire circumference, and the metal tube is bent while being heated by the high-frequency induction heating coil. It is assumed that.

Another method of bending a metal tube according to the present invention is to perform bending while heating the metal tube with a high-frequency induction heating coil. The temperature at any one of the two sides is maintained at a target temperature by controlling the high-frequency heating power, while the difference between the target temperature and the temperature at the position facing the same and the bending deformation of the heating portion of the metal tube.
The difference between the ventral and dorsal sides of the shape and the temperature at opposing positions shifted by about 90 degrees from each other is taken, and the position of the high-frequency induction heating coil is controlled by these temperature differences, and the metal tube In this method, the metal tube is bent while being heated by a high-frequency induction heating coil by making the circumferential temperature of the heating section equal to the target temperature over the entire circumference.

One of the metal pipe bending apparatuses of the present invention for implementing one of the above-described metal pipe bending methods is an apparatus for bending a metal pipe while heating it with a high-frequency induction heating coil. A first radiation thermometer that is attached to the high-frequency induction heating coil and measures the ventral (or dorsal) temperature of the bending deformation of the heating portion of the metal tube, and the second radiation thermometer that measures the dorsal (or ventral) temperature A radiation thermometer and a temperature measurement result of the first radiation thermometer are input, and an output corresponding to a deviation from a target temperature is output to a high frequency generator to target a ventral (or dorsal) temperature of bending deformation. A first temperature controller that controls the high-frequency generator so as to match the temperature, and a calculator that receives the temperature measurement results of the first radiation thermometer and the second radiation thermometer and calculates and outputs the temperature difference, The output of the computing unit is input and a preset temperature difference A second temperature controller for outputting a deviation, an inverter set to a frequency corresponding to an input from the second temperature controller, and a lateral movement of the high-frequency induction heating coil by an input from the second temperature controller. A sequencer for calculating a distance and outputting a rotation direction and a start command of a geared motor for moving the high-frequency induction heating coil in a screw feed mode to the inverter.

Another embodiment of the metal pipe bending apparatus of the present invention for carrying out another one of the above metal pipe bending methods is the high frequency induction machine according to the above metal pipe bending apparatus. Bending deformation of the heating part of the metal tube attached to the heating coil
A third radiation thermometer and a fourth radiation thermometer that measure the temperature of the abdominal and dorsal sides and the position at the opposite position shifted by about 90 degrees ,
A second computing unit that receives the temperature measurement results of the third radiation thermometer and the fourth radiation thermometer and calculates and outputs the temperature difference between the second and third computing units. A third temperature controller that outputs a deviation, a second inverter that is set to a frequency corresponding to the input from the third temperature controller, and a longitudinal direction of the high-frequency induction heating coil that is also input by the third temperature controller. And a second sequencer that outputs a rotation direction and a start command of a second geared motor that calculates the moving distance of the second high-frequency induction heating coil and moves the high-frequency induction heating coil vertically in a screw feed manner to the second inverter. It is assumed that.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method and apparatus for bending a metal pipe according to the present invention will be described.

First, one of the bending apparatuses for performing one of the bending methods of the metal pipe will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a metal tube to be bent. The metal tube 1 is inserted into a high-frequency induction heating coil 2 having a nozzle for spraying a cooling liquid 3 as shown in FIG. Is gripped by the clamp 5 on the bending arm 4 that pivots about the fulcrum 0.

A first radiation thermometer 6 for measuring the temperature on the ventral side of the bending deformation of a portion of the metal tube 1 shown in FIG. 1 which is heated by the high-frequency induction heating coil 2, and a second temperature for measuring the temperature on the back side. A radiation thermometer 7 is attached to the heating coil 2 via a heat-insulating support 9 at a symmetrical position of the heating coil 2 toward a through hole 8 penetrating from the outer peripheral surface to the inner peripheral surface. The first radiation thermometer 6 is connected to an amplifier circuit 10 for amplifying a signal of the measured temperature, and the amplifier circuit 10 is connected to a first temperature controller 11. The first temperature controller 11 outputs a deviation between the measured temperature signal amplified and input by the amplifier circuit 10 and a preset target temperature signal to the high-frequency generator 12, and outputs the temperature on the ventral side of the bending deformation. The heating power of the high-frequency generator 12 is controlled so that is equal to the target temperature. Numeral 13 denotes an arithmetic unit. The arithmetic unit 13 amplifies the temperature signal measured by the first radiation thermometer 6 by the amplifier circuit 10 and inputs the measured temperature signal and the temperature measured by the second radiation thermometer 7. The signal is amplified by the amplifier circuit 14 and a temperature difference is calculated based on the measured temperature signal input and output. 1
Reference numeral 5 denotes a second temperature controller which is connected to the calculator 13 and outputs a deviation between the temperature difference input from the calculator 13 and a preset temperature difference. An inverter 16 is connected to the second temperature controller 15 and is set to a frequency corresponding to an input from the second temperature controller 15. Numeral 17 is also connected to the second temperature controller 15 to calculate the lateral movement distance of the heating coil 2 based on the input from the second temperature controller 15 and to move the heating coil 2 in the screw feed system in the lateral direction. The sequencer outputs a rotation direction and a start command of a geared motor 18 as a driving source to the inverter 16.
The heating coil 2 has a slit arm 19 with an insulating material interposed.
Are connected and supported by a booth bar 21 of a transformer 20, and a base 22 on which the transformer 20 is installed and fixed is connected to a lower support 23
It is supported on a ball screw shaft 24 driven by forward and reverse rotation of the upper gear motor 18 so as to be movable in the lateral direction.

One embodiment of the bending method according to the present invention for bending the metal tube 1 using the bending apparatus having the above-described configuration will be described. The metal tube 1 is inserted into the high-frequency induction heating coil 2. As shown in FIG. 3, the distal end is gripped by the bending arm 4 with the clamp 5, and the metal tube 1 is advanced while the metal tube 1 is heated to a narrow annular width by the heating coil 2, and the bending is performed by turning the bending arm 4. In processing
The temperature of one point on the belly side of the bending deformation of the heating portion of the metal tube 1 is measured by the first radiation thermometer 6, and the signal of the measured temperature is amplified by the amplifier circuit 10 and sent to the first temperature controller 11. The first temperature controller 11 outputs a deviation between the input measured temperature signal and a preset target temperature signal to the high frequency generator 12, so that the high frequency generator 12 controls the high frequency heating power for the heating coil 2. Then, the temperature at one point on the ventral side of the bending deformation is set as the target temperature. On the other hand, the temperature on the back side of the bending deformation facing this target temperature is measured by the second radiation thermometer 7,
The signal of the measured temperature is amplified by the amplifier circuit 14 and the arithmetic unit 1
Send to 3. The calculator 13 calculates a temperature difference based on the measured temperature signal input from the first radiation thermometer 6 and the measured temperature signal input from the second radiation thermometer 7, and calculates the temperature difference as a second temperature controller. 15 is output. The second temperature controller 15 outputs a difference between the temperature difference input from the arithmetic unit 13 and a preset temperature difference to the inverter 16, so that the inverter 16 is set to a frequency corresponding to the difference. The deviation output from the second temperature controller 15 is also input to the sequencer 17, where the movement distance of the heating coil 2 in the lateral direction is calculated, and a gear motor 18 which is a driving source for laterally moving the heating coil 2 in a screw feed system. Is output to the inverter 16. As a result, the inverter 16 starts the rotation of the geared motor 18 and starts the forward or reverse rotation, rotates the ball screw shaft 24 in the same direction, moves the base 22 on the ball screw shaft 24 in the lateral direction by a predetermined distance, and The heating coil 2 connected and supported by the booth bar 21 of the transformer 20 is integrally moved in the lateral direction by a predetermined distance,
The position of the heating coil 2 is controlled, and the circumferential direction of the heating portion of the metal tube 1 is bent by the heating coil 2 while being heated to the target temperature equally over the entire circumference. The temperature control and the position control of the heating coil 2 are continuously performed until the bending of the metal tube 1 is completed. The temperature control and the position control complement each other with respect to a change in conditions due to the progress of bending, and the target temperature is maintained. Dripping.

Next, another embodiment of a bending apparatus for implementing another method of bending a metal pipe will be described with reference to FIG. In this bending apparatus, in addition to the bending apparatus described above, the phase of the metal tube 1 heated by the high-frequency induction heating coil 2 is substantially 90 degrees in phase with the ventral and dorsal sides of the bending deformation.
A third radiation thermometer 25 and a fourth radiation thermometer 26 for measuring the temperature of the displaced and opposed positions are heated at the upper and lower positions of the heating coil 2 from the outer peripheral surface to the through hole 8 penetrating through the inner peripheral surface. It is attached to the coil 2 via a heat insulating support 9. The third radiation thermometer 25 and the fourth radiation thermometer 26 are amplifier circuits 27 and 28 for amplifying the signal of the measured temperature, respectively.
, And the amplifier circuits 27 and 28 are connected to a second computing unit 29 which inputs the measured temperature signal, calculates and outputs the temperature difference,
The second computing unit 29 is connected to a third temperature controller 30 that outputs according to a difference between the input temperature difference and a preset temperature difference. 31 is connected to the third temperature controller 30;
The second inverter is set to a frequency according to the input from the third temperature controller 30. Numeral 32 is also connected to the third temperature controller 30 to calculate the vertical movement distance of the heating coil 2 based on the input from the third temperature controller 30 and to move the heating coil 2 in the screw feed system in the vertical direction. The second sequencer outputs a rotation direction and a start command of the second geared motor 33 as a driving source to the second inverter 31. The heating coil 2 is the same as the above-described bending apparatus in that a slit arm 19 with an insulating material interposed is connected to and supported by a booth bar 21 of a transformer 20. Is mounted and fixed on a receiving base 35 movably supported in a vertical direction on a ball screw shaft 34 driven by the
Is provided on a vertical wall 22a of a base 22, and the base 22 is supported movably in a lateral direction on a ball screw shaft 24 driven by forward and reverse rotation of a gear motor 18 on a lower support 23.

Another embodiment of the bending method of the present invention for bending the metal tube 1 by using the bending apparatus configured as described above will be described. The metal tube 1 is inserted into the high-frequency induction heating coil 2. Then, as shown in FIG. 3, the bending arm 4 is gripped by the clamp 5 and the metal tube 1 is moved forward while the heating coil 2 heats the metal tube 1 to an annular narrow width. In the bending process, the temperature of one point on the ventral side of the bending deformation of the heating portion of the metal tube 1 is set to the target temperature by the same control as in the above-described bending method. On the other hand, the temperature on the back side of the bending deformation facing this target temperature is measured by the second radiation thermometer 7 in the same manner as in the above-described bending method, and the signal of the measured temperature is amplified by the amplifier circuit 14 and calculated. To the vessel 13. The calculator 13 calculates a temperature difference based on the measured temperature signal input from the first radiation thermometer 6 and the measured temperature signal input from the second radiation thermometer 7, and calculates the temperature difference as a second temperature controller. 15 is output. In the second temperature controller 15, the difference between the temperature difference input from the calculator 13 and the preset temperature difference is calculated by the inverter 16.
, The inverter 16 is set to a frequency corresponding to the deviation. The deviation output from the second temperature controller 15 is also input to the sequencer 17, where the movement distance of the heating coil 2 in the horizontal direction is calculated, and the rotation of the gear motor 18, which is a driving source for moving the heating coil 2 in the horizontal direction, is performed. A direction and start command are output to the inverter 16. As a result, the inverter 16 starts the rotation of the gear motor 18 in the forward or reverse direction, rotates the ball screw shaft 24 in the same direction, moves the base 22 on the ball screw shaft 24 in the lateral direction by a predetermined distance, and The heating coil 2 connected and supported by the booth bar 21 of the transformer 20 on the receiving table 35 supported on the vertical wall 22a by the ball screw shaft 34 so as to be movable in the vertical direction is integrally moved in the horizontal direction by a predetermined distance.

Similarly, bending deformation of the heating portion of the metal tube 1
The temperature at the position opposite to the ventral side and the back side of the radiator by approximately 90 degrees is measured by the third radiation thermometer 25 and the fourth radiation thermometer 2.
6, and the signals of the measured temperatures are respectively amplified by the amplifier circuits 2.
At 7 and 28, the signal is amplified and sent to the second computing unit 29. The second calculator 29 calculates a temperature difference based on the measured temperature signal input from the third radiation thermometer 25 and the measured temperature signal input from the fourth radiation thermometer 26, and calculates the temperature difference as a third temperature. Output to the controller 30. The third temperature controller 30 outputs the difference between the temperature difference input from the second computing unit 29 and the preset temperature difference to the second inverter 31. As a result, the second inverter 31 sets a frequency corresponding to the difference. Is done. The deviation output from the third temperature controller 30 is also input to the second sequencer 32, where the vertical movement distance of the heating coil 2 is calculated, and the second driving source, which is a driving source for moving the heating coil 2 in the vertical direction, is calculated. A rotation direction of the geared motor 33 and a start command are output to the second inverter 31. As a result, the second inverter 31 starts the forward or reverse rotation with the start of the second geared motor 33, rotates the ball screw shaft 34 in the same direction, and moves the cradle 35 on the ball screw shaft 34 in the vertical direction by a predetermined distance. Then, the booth bar 21 of the transformer 20 on the receiving stand 35
The heating coil 2 connected to and supported by the moving member is integrally moved by a predetermined distance in the vertical direction.

In this manner, the heating coil 2 is moved in the horizontal and vertical directions by a predetermined distance to control the position of the heating coil 2 so that the circumferential direction of the heating portion of the metal tube 1 is made equal by the heating coil 2 over the entire circumference. Bending while heating to the target temperature. The temperature control and the position control of the heating coil 2 are continuously performed until the bending of the metal tube 1 is completed. The temperature control and the position control complement each other with respect to a change in conditions due to the progress of bending, and the target temperature is maintained. Dripping. In particular, as described above, the heating section of the metal tube 1
Relative phase shifted approximately 90 degrees from ventral and dorsal sides of bending deformation
If the position of the heating coil 2 is also moved in the vertical direction to control the temperature at the position to
The temperature of the entire circumference of the heating section can be accurately set to the target temperature.

In the method of bending two metal tubes according to the present invention, the heating coil 2 is controlled by controlling the position of the heating coil 2 in the horizontal and vertical directions.
And the metal tube 1 may come into contact with each other, and furthermore, the external shape of the heating portion formed by bending the metal tube 1 becomes longer and shorter in the horizontal direction and becomes flat, and the metal tube 1 is deformed by the bending direction. Since there is a possibility of contact with the heating coil 2, a sensor that directly measures the positional relationship between the heating coil 2 and the metal tube 1 and detects the contact is used. Of course, since the metal part of the sensor is heated by high frequency and cannot be used, the copper tube is air-cooled and the copper tube and the metal tube 1 are cooled.
It is preferable to sense a contact between the heating coil 2 and the metal tube 1 by providing a potential between them and performing switching by contact between the two.

[0019]

As can be seen from the above description, according to the metal pipe bending method of the present invention, when the metal pipe is bent while being heated by the high-frequency induction heating coil, the entire circumference of the heating portion of the metal pipe is heated. Since the temperature can be accurately controlled to the target temperature, the structure of the bent portion can be made uniform.

Further, according to the metal pipe bending apparatus of the present invention, the bending method exhibiting the above-described excellent effects can be performed smoothly and appropriately accurately.

[Brief description of the drawings]

FIG. 1 is a diagram showing a bending apparatus for performing one of the bending methods of a metal pipe according to the present invention.

FIG. 2 is a view showing a bending apparatus for carrying out another method of bending a metal pipe according to the present invention.

FIG. 3 is an explanatory view of a general metal pipe bending method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal tube 2 High frequency induction heating coil 3 Coolant 4 Bending arm 5 Clamp 6 First radiation thermometer 7 Second radiation thermometer 10 Amplification circuit 11 First temperature controller 12 High frequency generator 13 Computing unit 14 Amplification circuit 15 Second Temperature controller 16 Inverter 17 Sequencer 18 Gear motor 24 Ball screw shaft 25 Third radiation thermometer 26 Fourth radiation thermometer 27, 28 Amplification circuit 29 Second computing unit 30 Third temperature controller 31 Second inverter 32 Second sequencer 33 Second gear motor 34 Ball screw shaft

Claims (4)

(57) [Claims] When a metal tube is bent while being heated by a high-frequency induction heating coil, the temperature of one of an abdominal side and a back side of bending deformation of a heating portion of the metal tube is controlled by controlling high-frequency heating power. By maintaining the target temperature, the difference between the target temperature and the temperature at the position facing the target temperature is determined, and the position of the high-frequency induction heating coil is controlled by the temperature difference, and the temperature in the circumferential direction of the heating portion of the metal tube is set to the target temperature. A method for bending a metal tube, wherein the metal tube is bent while being heated at a temperature equal to the entire circumference and heated by a high-frequency induction heating coil. 2. A method of controlling a high-frequency heating power by heating a metal tube by a high-frequency induction heating coil while bending the metal tube at one point on the abdominal or back side of the bending deformation of the heating portion of the metal tube. To the target temperature, while the difference between the target temperature and the temperature at the position facing the
A phase that is approximately 90 degrees out of phase with the ventral and dorsal sides of the bending deformation
The difference between the temperature at the opposing position is taken, the position of the high-frequency induction heating coil is controlled by these temperature differences, the temperature in the circumferential direction of the heating section of the metal tube is made equal to the target temperature over the entire circumference, and the metal tube is heated. A metal tube by a high-frequency induction heating coil. 3. An apparatus for bending a metal tube while heating the metal tube with a high-frequency induction heating coil, wherein a temperature of a belly side or a back side of bending deformation of a heating portion of the metal tube attached to the high-frequency induction heating coil is measured. A first radiation thermometer and a second radiation thermometer for measuring the temperature of the back or the abdomen, and a temperature measurement result of the first radiation thermometer is input and an output corresponding to a deviation from a target temperature is output to the high frequency generator. And a first temperature controller for controlling the high-frequency generator so that the temperature on the abdominal or back side of the bending deformation matches the target temperature, and measuring the temperature of the first radiation thermometer and the second radiation thermometer. A computing unit to which the result is inputted and computes and outputs the temperature difference, a second temperature regulator to which the output of the computing unit is inputted and outputs a deviation from a preset temperature difference, and And the inverter set to the frequency according to the input of Similarly, the rotation direction and the start command of the geared motor that horizontally moves the high-frequency induction heating coil in the screw feed mode by calculating the lateral movement distance of the high-frequency induction heating coil based on the input from the second temperature controller are sent to the inverter. A bending device for a metal pipe, comprising: a sequencer for outputting to a metal pipe. 4. A metal pipe bending apparatus according to claim 3, wherein the heating section of the metal pipe is attached to the high-frequency induction heating coil, and the heating section of the metal pipe is shifted by approximately 90 degrees in phase from the ventral side and the back side.
And a third radiation thermometer and a fourth radiation thermometer for measuring the temperature at the opposed positions, and the temperature measurement results of the third radiation thermometer and the fourth radiation thermometer are input, and the difference between the temperatures is calculated and output. A second computing unit, a third temperature regulator to which an output of the second computing unit is input and outputs a deviation from a preset temperature difference, and a frequency set according to an input from the third temperature regulator. The second inverter and the rotation of the second geared motor that calculates the vertical moving distance of the high-frequency induction heating coil in the same manner as the input from the third temperature controller and moves the high-frequency induction heating coil in the screw feed system in the vertical direction. A second sequencer for outputting a direction and a start command to the second inverter.